RESUMO
Intestinal bacterial ß-glucuronidase (ßG) hydrolyzes glucuronidated metabolites to their toxic form in intestines, resulting in intestinal damage. The development of a method to inhibit ßG is thus important but has been limited by the difficulty of directly assessing enzyme activity in live animals. Here, we utilized a fluorescent probe, fluorescein di-ß-D-glucuronide (FDGlcU), to non-invasively image the intestinal bacterial ßG activity in nude mice. In vitro cell-based assays showed that the detection limit is 104 colony-forming units/well of ßG-expressing bacteria, and that 7.81 ng/mL of FDGlcU is enough to generate significant fluorescent signal. In whole-body optical images of nude mice, the maximum fluorescence signal for ßG activity in intestines was detected 3 hours after gavage with FDGlcU. Following pretreatment with a bacterial ßG inhibitor, the fluorescence signal was significantly reduced in abdomens and excised intestines images. For a 4-day antibiotic treatment to deplete intestinal bacteria, the FDGlcU-based images showed that the ßG activity was decreased by 8.5-fold on day 4 and then gradually increased after treatment stopped. The results suggested that FDGlcU-based imaging revealed the in vitro and in vivo activity of intestinal bacterial ßG, which would facilitate pharmacodynamic studies of specific bacterial ßG inhibitors in animal studies.
